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## -*- tcl -*-
# ### ### ### ######### ######### #########
## Common information for slippy based maps. I.e. tile size,
## relationship between zoom level and map size, etc.
## See http://wiki.openstreetmap.org/wiki/Slippy_map_tilenames#Pseudo-Code
## for the coordinate conversions and other information.
# ### ### ### ######### ######### #########
## Requisites
package require Tcl 8.4
package require snit
package require math::constants
# ### ### ### ######### ######### #########
## Implementation
namespace eval ::map::slippy {
math::constants::constants pi radtodeg degtorad
}
snit::type map::slippy {
# ### ### ### ######### ######### #########
## API
typemethod length {level} {
return [expr {$ourtilesize * [tiles $level]}]
}
typemethod tiles {level} {
return [tiles $level]
}
typemethod {tile size} {} {
return $ourtilesize
}
typemethod {tile valid} {tile levels {msgv {}}} {
if {$msgv ne ""} { upvar 1 $msgv msg }
# Bad syntax.
if {[llength $tile] != 3} {
set msg "Bad tile <[join $tile ,]>, expected 3 elements (zoom, row, col)"
return 0
}
foreach {z r c} $tile break
# Requests outside of the valid ranges are rejected
# immediately, without even going to the filesystem or
# provider.
if {($z < 0) || ($z >= $levels)} {
set msg "Bad zoom level '$z' (max: $levels)"
return 0
}
set tiles [tiles $z]
if {($r < 0) || ($r >= $tiles) ||
($c < 0) || ($c >= $tiles)
} {
set msg "Bad cell '$r $c' (max: $tiles)"
return 0
}
return 1
}
# Coordinate conversions.
# geo = zoom, latitude, longitude
# tile = zoom, row, column
# point = zoom, y, x
typemethod {geo 2tile} {geo} {
::variable degtorad
::variable pi
foreach {zoom lat lon} $geo break
# lat, lon are in degrees.
# The missing sec() function is computed using the 1/cos equivalency.
set tiles [tiles $zoom]
set latrad [expr {$degtorad * $lat}]
set row [expr {int((1 - (log(tan($latrad) + 1.0/cos($latrad)) / $pi)) / 2 * $tiles)}]
set col [expr {int((($lon + 180.0) / 360.0) * $tiles)}]
return [list $zoom $row $col]
}
typemethod {geo 2tile.float} {geo} {
::variable degtorad
::variable pi
foreach {zoom lat lon} $geo break
# lat, lon are in degrees.
# The missing sec() function is computed using the 1/cos equivalency.
set tiles [tiles $zoom]
set latrad [expr {$degtorad * $lat}]
set row [expr {(1 - (log(tan($latrad) + 1.0/cos($latrad)) / $pi)) / 2 * $tiles}]
set col [expr {(($lon + 180.0) / 360.0) * $tiles}]
return [list $zoom $row $col]
}
typemethod {geo 2point} {geo} {
::variable degtorad
::variable pi
foreach {zoom lat lon} $geo break
# Essence: [geo 2tile $geo] * $ourtilesize, with 'geo 2tile' inlined.
set tiles [tiles $zoom]
set latrad [expr {$degtorad * $lat}]
set y [expr {$ourtilesize * ((1 - (log(tan($latrad) + 1.0/cos($latrad)) / $pi)) / 2 * $tiles)}]
set x [expr {$ourtilesize * ((($lon + 180.0) / 360.0) * $tiles)}]
return [list $zoom $y $x]
}
typemethod {tile 2geo} {tile} {
::variable radtodeg
::variable pi
foreach {zoom row col} $tile break
# Note: For integer row/col the geo location is for the upper
# left corner of the tile. To get the geo location of
# the center simply add 0.5 to the row/col values.
set tiles [tiles $zoom]
set lat [expr {$radtodeg * (atan(sinh($pi * (1 - 2 * $row / double($tiles)))))}]
set lon [expr {$col / double($tiles) * 360.0 - 180.0}]
return [list $zoom $lat $lon]
}
typemethod {tile 2point} {tile} {
foreach {zoom row col} $tile break
# Note: For integer row/col the pixel location is for the
# upper left corner of the tile. To get the pixel
# location of the center simply add 0.5 to the row/col
# values.
#set tiles [tiles $zoom]
set y [expr {$ourtilesize * $row}]
set x [expr {$ourtilesize * $col}]
return [list $zoom $y $x]
}
typemethod {point 2geo} {point} {
::variable radtodeg
::variable pi
foreach {zoom y x} $point break
set length [expr {$ourtilesize * [tiles $zoom]}]
set lat [expr {$radtodeg * (atan(sinh($pi * (1 - 2 * double($y) / $length))))}]
set lon [expr {double($x) / $length * 360.0 - 180.0}]
return [list $zoom $lat $lon]
}
typemethod {point 2tile} {point} {
foreach {zoom y x} $point break
#set tiles [tiles $zoom]
set row [expr {double($y) / $ourtilesize}]
set col [expr {double($x) / $ourtilesize}]
return [list $zoom $row $col]
}
typemethod {fit geobox} {canvdim geobox zmin zmax} {
foreach {canvw canvh} $canvdim break
foreach {lat0 lat1 lon0 lon1} $geobox break
# NOTE we assume ourtilesize == [map::slippy length 0].
# Further, we assume that each zoom step "grows" the
# linear resolution by 2 (that's the log(2) down there)
set canvw [expr {abs($canvw)}]
set canvh [expr {abs($canvh)}]
set z [expr {int(log(min( \
($canvh/$ourtilesize) / (abs($lat1 - $lat0)/180), \
($canvw/$ourtilesize) / (abs($lon1 - $lon0)/360))) \
/ log(2))}]
# clamp $z
set z [expr {($z<$zmin) ? $zmin : (($z>$zmax) ? $zmax : $z)}]
# Now $zoom is an approximation, since the scale factor isn't uniform
# across the map (the vertical dimension depends on latitude). So we have
# to refine iteratively (I expect it to take just one step):
while {1} {
# Now we can run "uphill", then there's z0 = z - 1 and "downhill",
# then there's z1 = z + 1 (from the last iteration)
#puts "try zoom $z"
foreach {_ y0 x0} [map::slippy geo 2point [list $z $lat0 $lon0]] break
foreach {_ y1 x1} [map::slippy geo 2point [list $z $lat1 $lon1]] break
set w [expr {abs($x1 - $x0)}]
set h [expr {abs($y1 - $y0)}]
if { $w > $canvw || $h > $canvh } {
# too big: shrink
#puts "too big: shrink..."
if { [info exists z0] } break; # but not if we come "from below"
if {$z <= $zmin} break; # can't be < $zmin
set z1 $z
incr z -1
} else {
# fits: grow
#puts "fits: grow..."
if { [info exists z1] } break; # but not if we come "from above"
set z0 $z
incr z
}
}
if { [info exists z0] } { return $z0 }
return $z
}
proc tiles {level} {
return [expr {1 << $level}]
}
# ### ### ### ######### ######### #########
## Internal commands
# ### ### ### ######### ######### #########
## State
typevariable ourtilesize 256 ; # Size of slippy tiles <pixels>
# ### ### ### ######### ######### #########
}
# ### ### ### ######### ######### #########
## Ready
package provide map::slippy 0.5
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